Schreiber et al., U.S. Pat. No. 5,092,424, the teachings of which are incorporated herein by reference, describes a specific speaker configuration which has the following advantages:
1. Relatively low average cone excursion in the bandpass region, i.e., relatively low distortion for large signal output for a given transducer size.
2. Relatively high output in this bandpass region for a given enclosure volume.
3. The use of common, practical, economically configured transducers as the drive units.
4. Relatively higher order rolloff of high frequencies.
5. Achievement of the bandpass characteristic without external electrical elements, resulting in relatively low cost, relatively high performance and relatively high reliability.
6. A transient response which is delaying in time by up to or greater than 10 milliseconds.
Schreiber et al. teach that these features may be used in any acoustic application where a bandpass output is desired, where low distortion is desired, where high output is desired, and/or where economically configured transducers are desired. The uses specified include, but are not limited to, bass boxes for musical instruments, permanently installed sound systems for homes or auditoria, and for nonlocalizable bass output components in multiple speaker configurations in which the desired sonic imaging is to be controlled by the higher frequency components of those multiple speaker configurations.
It is understood by the art that for any speaker system driven at high input electrical signal at a specified frequency, distortion components generated by the speaker system are generally higher in frequency than the specified frequency. If the specified frequency is in the bass region, these higher frequency distortion components make it easier for the listener to detect the speaker system location. In addition, most distortion has multiple frequency components resulting in a wideband distortion spectrum which gives multiple (positively interacting) clues to the listener as to the speaker system location. Because of the lower distortion generated by embodiments of this invention compared to prior art, these embodiments are more useful as nonlocalizable bass output components in multiple speaker configurations in which the desired sonic imaging is to be controlled by the higher frequency components of those multiple speaker configurations.
Generally speaking, it is also understood in the art that the higher order rolloff (&gt;/=18 dB/octave) of high frequencies for the component arrangement taught by Schreiber et al., enhances its nonlocalizability. Therefore, on complex signals (music or speech), the listener will receive significant directional cues only from the higher frequency components of the speaker system. Thus, costs of component arrangements are more useful than other arrangements as nonlocalizable bass output components in multiple speaker configurations in which the desired sonic imaging is to be controlled by the higher frequency components of those multiple speaker configurations.
As noted by Schreiber et al., prior experiments indicate that a listener's ability to correctly locate sources of sounds depends on the relative time difference of the sounds coming from those sources. If spectrally identical sounds are produced by two sources spaced a few meters apart, but one source produces the sound a few milliseconds later than the other, the listener will ignore the later source and identify the earlier source as the sole producer of both sounds (Precedence Effect). Thus, component arrangements such as those taught by Schreiber et al., and those of the present invention, produce a greater time delay than prior art and thus are more useful for providing nonlocalizable bass output components in multiple speaker configurations in which the desired sonic imaging is to be controlled by the higher frequency components of those multiple speaker configurations.